Method for treating household refuse

ABSTRACT

A method of treating household refuse in which the crushed and homogenized refuse is moistened and subjected to a compression in the order of 300 to 500 bars, the material under compression being traversed by perforated tubes for evacuating the liquids to form on the one hand liquid sludges extracted by the bores and on the other hand dry compressed substances. The installation for the treatment of household refuse comprises a storage tank, a device for mixing and homogenising the refuse, and immersion tank, a device for crushing and a press comprising perforated tubes for evacuating the liquids from the compression chamber.

United States Patent Boyer 1 Aug. 14, 1973 [54] METHOD FOR TREATING HOUSEHOLD 3,661.082 5/1972 a French et al loo/37 REFUSE FOREIGN PATENTS OR APPLICATIONS lnvemofi 2W9 Rue 533,296 9/1955 Italy 100/108 ognacq ay, ans, rance [22] Filed: Sept. 29, 1971 Primary Examiner-John Petrakes Assistant Examiner-Philip R. Coe [211 App! 184830 Attomey--Irvin S. Thompson et al.

2:; 3 38 A method of treating household refuse in which the p crushed and homogenized refuse is moistened and sub- [52] U S CI 100 I37 100 I39 100 /7 4 jected to a compression in the order of 300 to 500 bars,

d a 00 I215 loo/218 the material under compression being traversed by per- 51] 1m B'30b 9/04 forated tubes for evacuating the liquids to form on the [58] a 37 70 A one hand liquid sludges extracted by the bores and on 6 the other hand dry compressed substances. The installation for the treatment of household refuse comprises a storage tank, a device for mixing and homogenising [56] References Cited the refuse, and immersion tank, a device forcrushing UNITED STATES PATENTS and a press comprising perforated tubes for evacuating g lg s: the liquids from the compression chamber. un ea 3,583,01 l 6/1971 Maurer et a]. 100/73 X 8 Claims, 4 Drawing Figures Patented Aug. 14, 1973 3 Sheets-Sheet l Patented Aug. 14, 1973 3,752,059

3 Sheets-Sheet 2 Patented Aug. 14, 1973 3,752,059

3 Sheets-Sheet 5 METHOD FOR TREATING HOUSEHOLD REFUSE It has already been proposed to treat household refuse by crushing it and compressing it so as to form blocks which'may be covered with a protecting envelope or wrapped up in sealed or unsealed packages. The aim of this treatment is to transform the refuse into blocks, which are as stable as possible and capable of being stocked in a quarry, immersed or possibly used as filling or construction elements. It was also proposed to recover the liquids being discharged during compression these liquids constituting waste products or capable of being used as fertilizer.

Research carried out on these methods of compress ing household refuse has shown that they present numerous disadvantages. Firstly, the items of refuse being heterogeneous, the blocks which are obtained vary in size and rates of compression, thus prejudicing their subsequent utilisation. The mere discharge of liquid during compression permits a large number of substances which are easily washed away by water and which are essentially fermentable, to remain in the compressed mass. On the other hand, limited compressions, which are applied to blocks of refuse when blocks of uniform dimensions are required, reduce the density of the blocks in spite of the presence in the mass of water and heavy substances, which are easily carried away by water. Neither do they permit a me:

chanical destruction of the cells of bacteria and other micro-organisms to be obtained, as is the case with increased compression followed by a rapid expansion. Finally, the envelopes and packages do not prevent fermentation and provide only inadequate mechanical resistance of the finished block so that it is subject to cracking of the envelope followed by disintegration of the block.

It has also been proposed to dispose of refuse by incinerating it or by transforming it into compost. Incineration comes up against the fact that refuse is very rich in water and non-inflammable matter and on the other hand that it is very bulky. The incinerator must thus be very large and have complex grill systems to make the material move on. This material is first dried, which involves a considerable consumption of calories. Furthermore, the use of such a fuel lacks flexibility so that the energy yield is very low. Composts have the-disadvantage containing more and more non-fermentable substances useless as fertilizer which, on the other hand, possess a certain calorific power.g

The method, which forms the subject of the present invention has the aim of removing the above disadvantages. It is characterised in that the refuse, which has been crushed and homogenized is dampened and subjected to a compression of the order of 300 to 500 bars the mass being penetrated by perforated tubes for evacuating the liquids duringcompression.

It has been ascertained to an astonishing degree, that by moistening the mass in a homogeneous manner before compression and by facilitating the evacuation of liquids, a larger portion of fermentable organic substances capable of being destroyed by the bacteria, could be extracted from the mass of refuse. On the one hand, this results in liquid sludges being obtained, which are capable of being enriched by known methods and which form a much richer and more easily usable fertilizer than the standard compost, and, on the other hand, this results in a dry inert portion being obtained,

which is scarcely subject to fermentation, is odourless and in which the bacteria and micro-organisms have been substantially destroyed, in addition, this inert dry portion possesses negligible mechanical elasticity. By virtue of these characteristics, the dry, compressed mass may be stored, ground and caked with a binder so as to form, under reduced compression, blocks of specific size having an increased mechanical resistance or it may be used as a pulverised fuel in an incinerator. When the dry mass is caked to form blocks, the binder is preferably constituted by sodium silicate hardened with C0,. The hardening with CO, may be obtained by the injection of gas or better by adding cement to the binder giving off CO, as it solidifies.

According to another feature of the invention the sludges are subjected to a fermentation in a narrow bed with constant stirring for a period of about 4 to 5 hours in an enclosure at 60-70 C, said enclosure being traversed by an air current. This fermentation produces dry granules which are not subject to putrefaction or fermentation and which may be used as compost or dissolved in water to form a liquid fertilizer. The effluent gas is a mixture, which after washing to remove the water may be used as a fuel or as air charged with combustible gas to incinerate the solid deposits or for supplying the hot air generator of the fermentation installation.

On the other hand it has been ascertained that the dry substances contain a high percentage of cellulose fibres. Accordingly and in conformity with another feature these dry substances'are dispersed in a water bath containing 10-20 percent by weight of soda and, after maceration, the solids are separated and subjected to compression with the material in the course of compression traversed by perforated tubes for evacuating liquids.

The liquid part which is evacuated is a suspension of cellulose fibres which after concentration produces a paper paste. The dry part which is obtained after compression may be mixed with a binder and moulded to form blocks.

The installation for practicing the method comprises a storage cavity, a device for mixing and homogenizing the refuse, an immersion tank, a crushing device and a press having perforated tubes for evacuating the liquids passing through the compression chamber.

According to a perferred embodiment the installation comprises a double press with a conveyor bringing the refuse which has first been mixed and homogenized to a double grinder, which then distributes the refuse to two load feeders, the fixed casing of the grinder having helically disposed blades, forming the'immersion tank for dampening the refuse, the load feeders being positioned above the two compression chambers disposed on either side of a central jack, the upper part of eachcompression chamber being closed by a swinging door cramming the refuse into the said chamber, the base of the chamber having apertures for the passage of the perforated tubes for evacuating the liquids and the lower wall of the chamber having a flap valve for removing the compressed block, the pistons acting in the said chambers each being integral with the opposite rod of the piston of the double acting central jack.

It is possible to control the separation of the dry substances and consequently the composition of the sediment by using perforated tubes with apertures of varying diameters. In this way it is possible to obtain dry substances, from which the decomposable substances have been almost totally removedwhich is essential when these dry substances have to be transformed into blocks or it is possible to obtain sludges which do not contain non-decomposable substances giving hence a rich compost, the decomposable part remaining in the dry substances causing only minor disadvantages when the dry substances are used as fuel.

These and other objects, features and advantages of the present invention will become apparent from a consideration of the following description, taken in connection with the accompanying drawings in which:

FIG. 1 is a comprehensive view in longitudinal crosssection of a compression installation;

FIG. 2 is a detailed view on a larger scale of the grinder on the right of FIG. 1;

FIG. 3 is a detailed view on a larger scale of a load feeder and its compression chamber;

FIG. 4 is a sectional view along IV-IV of FIG. 3.

The installation comprises a conveyor belt 1 which supplies it with refuse held in a storage cavity having been suitably mixed and homogenised. Preferably, metal parts and very hard materials, which are too large, are removed from the refuse. At the upper part of the conveyor the refuse falls into a crusher formed by two flanged crushers 2 turning in opposite directions. The crushed refuse falling from the crusher 2 is directed by an oscillating paddle 3 towards one or the other of the grinders. These two grinders are constituted (FIG. 2) by two shafts 4 driven by a central hydraulic motor 5 and supported at their free end by a bearing 6 integral with the casing 7 of the machine. Each shaft 4 bears grinder blades 8 helically disposed to make the refuse move forward in the grinder. Each shaft 4 is surrounded by a cylindrical housing 9 bearing fixed grinder fins 10. Metal sheets 11 are fixed at the two ends of this housing 9 and these close off the lower section of the cylindrical housing to form a tank for damping the refuse. The cylindrical housing 9 of the grinder is mounted so as to be mobile in the casing of the machine, according to the axial direction of the grinder this displacement being controlled by a jack 12. This possibility of displacement allows the fixed blades to be moved towards or away from the mobile blades to obtain a finer crushing or to allow foreign bodies, which are likely to block the grinder to pass through.

The crushed and moistened refuse issuing from the grinder falls into a feeder 13. The end wall of this feeder has a swining door 14. This door is formed by a frame 15 rotatably mounted about a shaft 16 and driven by a hydraulic motor 17. The frame comprises a cylindrical segment wall 18 and a closing plate 19 between the edge of the cylindrical segment wall 18 and the shaft 16.

In the open position (shown on the left in FIG. 1), the plate 19 seals the outer wall of the feeder 13, sealing at its upper part being ensured by a valve 20 articulated on the inner surface of the lateral wall of the feeder, the base of the feeder being, at this time, connected to the compression chamber, which will be described hereinafter. In the closed position (shown on the right in FIG. I), the plate 19 has turned so as to seal the base of the feeder, sealing being ensured by a sealing wedge 21 pushed against the corner edge of the plate 19 by the springs 22. The door is locked in position by the engagement of a key-pin 23 driven by a jack 24 into the bore hole of pin fitting 25 provided on the frame 15. Sealing on the lateral edges of the plate 19 is also effected by comer bars 26 provided on this plate 19 (FIG. 4) and these are acted upon by springs 27 so that they spread apart and cooperate with the inclined edges 28 of the aperture in the base of the feeder.

The compression chambers 29 are located below the aperture in the base of the feeder. Their upper surface is formed, at least in part, by the plate 19 of the swinging door in the closed position. The part of their lower surface adjacent to the base is also formed by a swinging door comprising a frame 30 rotatably mounted about a shaft 31 and driven by a hydraulic motor 32. The frame 30 is provided with a plate 33 with a chamfered edge which co-operates with the chamfered edge of the lower fixed wall 34 of the compression chamber. This swinging door is locked in a closed position by a key-pin 35 driven by a jack 36 and engaging in a bore hole of a pin fitting 37 integral with the frame 30.

In each of the chambers 29 a piston 38 is displaced by the rod 39, 40 of a double-acting jack 41. The cylinder of this jack 4] is mounted in the middle between the two compression chambers. The bottom wall of each chamber 29 comprises apertures 42 (four in the embodiment shown in FIGS.3 and 4) which extend by means of sealing sleeves 43 outside the chamber. Bores 44 in the form of perforated tubes are slidably mounted in these sleeves. These bores may be pushed into or extracted from the chamber 29 by the jacks 45. The ends of the bores are connected to tubes 46 which lead to a vacuum chamber (not shown). Conveyor belts 47 are mounted below the swinging doors 30 and these convey the compressed blocks to a central conveyor belt which removes them. The body of the jack 41 is mounted on the frame of the press by means of two pivots 49, which permit the cylinder of the jack to rotate, after the pistons have been disconnected and thus facilitate repairs.

The installation operates in the manner described hereinafter, certain operational details already having been described above. The mixed, sorted and homogenised refuse passes into the crusher 2 which destroys the hard bodies such as bottles, bits of stone, etc.. The flow of refuse is directed by the paddle 3 towards the grinder in which it is mangled and moistened. The refuse then falls into the feeder 13, the door 14 of which is closed, the plate 19 sealing the compression chamber 29. The piston 33 located below the feeder is drawn back by the jack 41. The door 30 is raised by the hydraulic motor 32 to close the lower wall of the compression chamber and is locked in the closed position by the key-pin 35 driven into the hole of the pin fitting 37 by the jack 36. At this moment the jack pulls back the key-pin 23 from the pin fitting 25 and the motor 17 causes the swing door 14 to pivot at the same time as the paddle 3 swings to direct the refuse towards the other feeder. As the upper wall of the compression chamber 29 is open the refuse falls into this chamber.

The hydraulic motor 17 then drives the door 14 in the opposite direction, thus forcing the refuse in the feeder into said chamber. When the plate 19 has sealed the wall of the compression chamber, the door 14 is locked in position by the key-pin 25. The bores 44 are plunged by the jacks 45 into the mass of refuse filling the chamber and the channels 46 are put under vacuum.

At this moment the jack 41 is supplied with power to plunge the piston 38 into the chamber 29. The bores 44 which withdraw in relation to the advance of the piston 38 extract a liquid sludge, the volume of which may be as much as 50 percent of the initial volume of the refuse. At the end of the stroke of the jack the compression reaches 500 bars and a block of dry substances is to be found compressed in the chamber above the swinging door 30. This swinging door is released, the jack 36 ensuring retraction of the key-pin 35. The door is swung by the hydraulic motor 32 to allow the block of dry substances to fall onto the conveyor 47, which transfers it to the conveyor 48, which discharges it.

The dry substances obtained constitute a virtually inert product havi ng, loose packed, a density greater than 1. The blocks of dry substances obtained were disintegrated and mixed with according to the quality required for the final block 4 to 20 percent in weight of sodium silicate, modulus 2 and with a 45 percent concentration and a percentage by weight of cement lower than the percentage by weight of the silicate but greater if more rapid setting is required. The mixture was then moulded under a pressure of 20 bars to obtain the blocks in their final form. As the dry matter is practically incapable of being compressed further, the blocks may be formed with accurate and stable dimensions. The cement ensures the giving off of C0,, which permits rapid setting of the sodium silicate. The blocks obtained have, after hardening, a mechanical resistance which varies with the quantity of the binder but which is generally between and 24 kg/cm and a density of about 1.1. It should be noted that if fermentation were to occur in the blocks, CO, would be produced, which would incrase the hardening of the silicate, thus preventing fermentation from developing. The blocks may be covered with a light layer of plastic or enveloped in asphalt.

The liquid sludges obtained are made up of substances which are very rapidly consumed by the bacteria they contain. Fermentation is rapid and produces a very rich fertilizer in contrast to the composts in which the bacteria have to destroy the dry substances.

in another case the block of dry substances obtained at the outlet of the press was disintegrated and the pulverulent product injected by a current of air into the combustion chamber of an incinerator where it burned like charcoal dust.

It is also possible according to another feature of the invention to subject the liquid sludges and the dry sub stances to special treatments for extracting products of value.

An example of an embodiment, at laboratory level, of these special treatments will be described, the figures given by way of indication being variable according to the nature of the refuse treated.

0.6 m of refuse of an approximate weight of 100 kg taken from a batch of refuse which had been homogenized and sorted to remove metal pieces and very big elements was subjected to humidification, and was chopped up and compressed by the method described above by a scale model of the press. About 60 litres weighing 60 kg ofliquid sludge and 0.04 m of dry substances of a total weight of approximately 44 kg were obtained.

5 kg of the liquid sludges were poured into a narrow bed in the tanks ofan experimental fermenter comprising an enclosed container, the content of the tanks being subjected to stirring by blade agitators. The container was maintained at a temperature of 65 C by passing through warm air at a rate of l m per hour with continuous extraction from the atmosphere by the fermenter. The tanks remained in the fermenter for 5 hours. During treatment the weight of the fermenter decreased progressively, becoming stable after 4 hours which indicated that fermentation had stopped. The washed gas extracts surrendered about 0.5 of a litre of water corresponding to the humidification water added to the raw refuse before compression and producing 5 kg of liquid sludge. The gaseous mixture evacuated was combustible and could be set alight. The dry substance remaining in the tanks was in the form of granules having a weight of about'l kg and forming an organic compost with a high fertilization value.

The 44 kg of dry substances were poured into a tank containing about 200 litres of water with 15 percent soda and, after maceration, they were subjected to compression in the same press as that used for compressing the refuse. The total weight of the bulk subjected to compression was about 53 kg. A dry sediment of about 22 kg was obtained after compression and this was crushed and caked together in the way described above so as to produce blocks containing substantially mineral and plastic substances and metallic elements which were not removed when the raw refuse was sorted. The 31 kg extracted in the form of a suspension were filtered to remove part of the soda solution which was returned to the maceration tank, the filtration cake constituting a paper paste which could be used for the manufacture of cardboard.

It was established that the method of treating refuse thus produced approximately 20 to 25 percent of dry substances capable of being transformed into construction blocks, 20 to 25 percent paper paste, 10 to 15 percent of organic granules forming a compost, a large quantity of combustible gas and water which is recycled into the installation for the humidification of refuse before compression. The combustible gas produced in the fermenter may be used to feed the hot air generator.

Although the present invention has been described and illustrated in connection with a preferred embodiment, it is to be understood that modifications and vari ations may be resorted to without departing from the spirit of the invention, as those skilled in this art will readily understand. Such modifications and variations are considered to be within the purview and scope of the present invention as defined by the appended claims. 7

Having described my invention, 1 claim:

1. A method of treating household refuse, comprising crushing and homogenizing the refuse, moistening the crushed and homogenized refuse with water, inserting perforated tubes into the moistened ref se and s ubjecting the moistened refuse to a compression of at least about 300 bars, and withdrawing through said tubes liquid sludges expressed from said refuse during said compression leaving dry compressed substances.

2. A method for treating household refuse according to claim 1, in which the dry substances are dispersed in a water bath containing 10 to 20 percent in weight of soda and, after maceration, the material is taken out and subjected to compression with the material in the course of compression traversed by perforated tubes for evacuating liquids, the liquid part being evacuated being concentrated to form a paper past and the residue constituting a new dry substance.

3. A method of treating household refuse according to claim 2, in which the dry substances obtained at the end of compression are mixed with a binder and moulded under a pressure of 20 bars.

4. A method of treating household refuse according to claim 3, in which the binder is constituted by silicate of soda hardened with (30 if r 5. A method of treating household refuse according to claim 4, in which the hardening of the silicate is ensured by the addition of cement to the mixture of dry substances and silicate.

6. A method of treating household refuse according to claim 1, in which the liquid sludges are subjected to a fermentation in a narrow bed under constant stirring for a period of about 4-5 hours in a container at 60-70 C through which flows an air current to pror molded under a pressure of 20 bars. 

1. A method of treating household refuse, comprising crushing and homogenizing the refuse, moistening the crushed and homogenized refuse with water, inserting perforated tubes into the moistened ref se and s ubjecting the moistened refuse to a compression of at least about 300 bars, and withdrawing through said tubes liquid sludges expressed from said refuse during said compression leaving dry compressed substances.
 2. A method for treating household refuse according to claim 1, in which the dry substances are dispersed in a water bath containing 10 to 20 percent in weight of soda and, after maceration, the material is taken out and subjected to compression with the material in the course of compression traversed by perforated tubes for evacuating liquids, the liquid part being evacuated being concentrated to form a paper past and the residue constituting a new dry substance.
 3. A method of treating household refuse according to claim 2, in which the dry substances obtained at the end of compression are mixed with a binder and moulded under a pressure of 20 bars.
 4. A method of treating household refuse according to claim 3, in which the binder is constituted by silicate of soda hardened with CO2.
 5. A method of treating household refuse according to claim 4, in which the hardening of the silicate is ensured by the addition of cement to the mixture of dry substances and silicate.
 6. A method of treating household refuse according to claim 1, in which the liquid sludges are subjected to a fermentation in a narrow bed under constant stirring for a period of about 4-5 hours in a container at 60*-70* C through which flows an air current to produce a powdered compost and a combustible gas.
 7. A method of treating household refuse according to claim 1, in which the dry substances obtained at the end of compression are powdered and used as fuel.
 8. A method for treating household refuse according to claim 1, in which the dry substances obtained at the end of compression are mixed with a binder and molded under a pressure of 20 bars. 